1. Field of the Invention
This invention relates to an auxiliary power supply and timer arrangement for AC electric energy meters including a programmable time based measuring system for performing multiple metering operations and relating such operations to real time, and further to such an alternate arrangement including a secondary timer circuit and an auxiliary DC supply having a non-rechargeable battery capable of maintaining a real time record and non-volatile metering data during power outage interruptions reoccurring over the extended and unattended service life of the meter.
2. Description of the Prior Art:
Electric energy billing meters of the electromechanical type are well known for their extensive use at the premises of separate users of electric energy. The meters establish the amount of electric energy consumption for billing by the electric energy supplier. Most universally used billing meters provide for measuring the total consumption of electric energy or a maximum peak demand which requires a manual resetting operation, typically once each month. Increased flexibility in measuring different parameters such as measuring both kilowatt hour consumption and kilowatt demand at different rates, is often desired. Also desired is to separately totalize the different measured parameters as they are measured during different designated time intervals during each day. This method of metering is known as time-of-day metering by those skilled in the art. The designated time-of-day intervals typically correspond to tohose times at which the levels of demand for energy from an energy supplier, such as an electric utility, is at a highest, or intermediate, or low level.
Induction watthour meters equipped with mechanical multi-dual kilowatt hour registers or combined kilowatt hour and watt demand registers are known and selective operation of separate sets of register dials are known to be provided in response to mechanical time switch mechanisms. The aforementioned registers and mechanical time mechanisms have only a few different measuring capabilities and are often limited as to the different time intervals which may be provided and such intervals are generally not variable as between weekdays and weekend days. In U.S. Pat. No. 4,077,061 for a Digital Processing And Calculating AC Electric Energy Metering System, issued Feb. 28, 1978, and assigned to the assignee of this invention a programmable electronic calculating circuit is disclosed for providing large flexibility in measuring several different parameters of an electric energy quantity. The measured parameters are quantized and recorded values thereof are non-volatively magnetically recorded with respect to time interval indications. The circuit does not develop an independent record of real time or accummulate a separate record of the different parameters when measured during different preselected daily time periods. There is disclosed a means of detecting interruption of an AC energized DC supply and for temporarily supplying a system after such a power interruption. No auxiliary DC supply is required for a random access data memory portion of the system which is capable of being reprogrammed from a read only memory in the system. A magnetic tape recorder for use with the aforementioned system does have a battery carryover circuit arrangement which may be as described in U.S. Pat. No. 3,538,406 issued Nov. 3, 1970, and assigned to the assignee of this invention.
In other electrical energy measuring systems where electronic times are utilized to generate current time for time-of-day data, the data is usually accumulated and stored in a non-volatile memory circuit requiring an uninterrupted supply of DC power. In the aforementioned systems, a source of time based signals are produced and totalized to represent each second, minute, hour and day of the week, for example. The systems may be preprogrammed to respond to different time intervals such as the same or different time periods each day, to totalize a given measured parameter of the electric energy quantity being measured. The measured parameters are separately related to a designated time interval each day. Kilowatthour consumption may be separately measured and totalized during designated high or on-peak time intervals, intermediate peak intervals or low or off peak time intervals. For such systems supplied by an AC energized DC supply, a failure of the AC source can cause loss of the stored time of day data in a volatile electronic memory. Interruptions in the operation of a time based signal generator will also occur. Where large numbers of meters having such electric energy measuring systems, it is impractical to go to each meter and update them to the current time. Alternate or standby DC supply circuits are required to maintain the systems operational for continuing to register current time and to retain the stored time data which has been accumulated up to the time of the power failure. U.S. Pat. No. 4,050,020 issued Sept. 20, 1977 discloses an electrical energy measuring system for measuring different preselected kilowatthour consumption periods each day. An auxiliary battery backup supply utilizes a rechargeable battery. The central control circuit thereof is battery energized to also energize an oscillator time base generator to continue real time recording during an outage of the main supply.
In U.S. Pat. No. 4,065,676 a battery backup system is disclosed utilizing a rechargeable battery for uninterrupted supply of DC voltage. No time-of-day recording is described in the last-named patent. In U.S. Pat. No. 3,937,890 a secondary power supply is disclosed to retain pulse counts accumulated in a volatile counter in an electric utility metering system upon failure of a main AC energized DC supply.
Accordingly, an improved auxiliary DC supply and secondary timer arrangement is desired for time registering electric energy metering system in which time-of-day data and electronic memory data is to be preserved when the main DC supply fails. Further desired is an auxiliary DC supply for such arrangements including a standby battery which is operable at a minimum current drain so that the battery does not have to be replaced or serviced in a meter including the system and having in-service times which may be in the order of several years and subject to widely varying operating conditions. A further desirable feature is to have a stand-by battery source that is capable of operating in ambient temperature extremes typically experienced by electric energy meters presently being used. The present invention is directed to achieve the above considerations in an economical and reliable manner.